This project aims to understand the role of long range forces on biological phenomena. A major topic has been the measurement of forces between phospholipid bilayer membranes immersed in water. We have recently succeeded in measuring intermolecular forces between lipids in the same membrane. Using the DCRT electronic display we have found two classes of forces between protein molecules forming dimers and tetramers (such as hemoglobin). An accurate procedure for calculating many body forces between spherical particles has been developed. BIBLIOGRAPHIC REFERENCES: Cowley, S., Fuller, N., Rand, R. P. and Parsegian, V.A.: Measurement of repulsion between charged phospholipid bilayers. Biophys. J. 17, 85a (1977). Gingell, D., Parsegian, V. A., Todd, I.: Experimental evidence for long-range attraction between a red cell and a hydrocarbon surface. Nature (in press) (1977).